Process for producing gasoline



Oct. 26, 1937. J. J. HOGAN PROCESS FOR PRODUCING GASOLINE Filed Feb. 1,1935 Wall @6063 INVENTOR. JAMESJl/OGA/V BY MM 2 ATTORNEY Patented Oct.26, 1937 UNITED STATES PATENT OFFICE James J. Hogan, Whiting, Ind.,assignor to Standard Oil Company, Chicago, 11]., a corporation ofIndiana Application February 1, 1935, Serial No. 4,509

6 Claims.

This invention relates to a process for the production of gasoline orother relatively light distillate from raw crude oil, or other similarrelatively heavy stock containing lighter and heavier constituents.

In the treatment of raw crude oil or the like to produce gasoline; ithas been a practice heretofore to distill from the crude oil bydistillation a distillate stock of gas oil nature and to subject thisdistillate stock to cracking treatment under conditions which willconvert a considerable portion thereof into hydrocarbons within thegasoline boiling range. Simultaneously during this distillation aplurality of other cuts or petroleum fractions may be separated from theoriginal crude oil such as, for example, light naphtha or virgingasoline, heavy naphtha, which may be reformed, kerosene and, in somecases, furnace oil. In certain instances the undistilled re duced crudefrom which some or all the distillate fractions above mentioned havebeen removed, has been subjected to a mild cracking treatment under Howcrack per pass conditions principally for the purpose of reducing itsviscosity and to form additional quantities of gas oil. The gas oil soformed has been then subjected to more drastic cracking treatment of thenature first mentioned so as to produce a further yield of gasolineconstituents.

One of the main objects of my invention is to provide a process for thetreatment of hydrocarbon oil, which may be raw, crude petroleum,

which will produce an improved yield of gasoline other desired endproducts from heavy hydrocarbon oil stock, such as crude oil,whereincthe complete treatment may be carried out in simpier and morecompact apparatus with a consequent reduction in original installationexpense and in the continuing costs of operation.

Another and more specific object of my invenion is to provide a processfor treating hydrocarbon oil of the character hereinbefore mentionedwherein a heavy oil stock, which may be a topped or reduced crude,resulting from preliminary distillation of raw crude, maybe moreeifectively converted into cracking stock which can be subsequentlyconverted into a greater yield of gasoline or other desired lowerboiling hydrocarbons.

Other and more specific objects of my invention will become apparentfrom the more detailed description hereinafter.

The above and other objects will be attained by certain novel steps andcombination of steps 10 constituting my invention which will now bedescribed. I

In accordance with my invention a topped crude oil, or in other words acrude oil from" which the lower boiling constituents have been 15removed, or a heavy oil stock containing a preponderance of virginconstituents, is initially subjected to viscosity breaking, or mildcracking treatment, principally for producing intermediate gas oil stockwhich can be subsequently subjected to more drastic cracking treatment,and the products from the initial viscosity breaking treatment arefractionated to separate low boiling constituents including light gasoil. The remainder of the products resulting from the initial viscositybreaking treatment or in other words all of the heavier constituents ofthe viscosity broken products boiling above the light gas oil range,such as above 650 F. or 700 F. for example, are then subjected toadditional cracking or viscosity breaking treatment before finalseparation into end products and inter mediate fractions. It should beclear from the above that, in accordance with my invention, all

of the heavier constituents, of the original charging stock, boilingabove light gas oil, are subjected to at least two separate andindependent relatively mild cracking treatments before being separatedinto the final end products and intermed ate fractions and that all ofthe light gas oil formed in the process is subjected to relativelydrastic cracking conditions most'suitable for production of a h gh yieldof gasoline having high anti-knock properties.

In accordance with a more specific aspect of my invention, a toppedcrude or the like. substantially free of cracked products, is initiallysubjected to mild pyrolytic conversion, principally toform intermediategas oil cycle stock, and the products from said conversion treatment arethen introduced into an evaporator, into which other hot crackedproducts from the process are introduced, above an intermediate trap-outtray, which collects unvaporized constituents of the conversion productsand heavy gas oil condensate separated from the said converted productsand other cracked products introduced into the evaporator. The stockcollected in the intermediate trap-out tray is subjected to separatecracking treatment and the cracked products from the last-namedtreatment are also introduced into the evaporator, but below theintermediatetrapout tray, wherein the products separate into vapors andunvaporized residue. The vapors separated are then subjected to partialfractionation to condense the heavy gas oil constituents within theevaporator, which are collected in the intermediate trap-out tray andsubjected to said lastnamed cracking treatment. The unvaporized residueis withdrawn from the bottom of the evaporator and may be flashed to afinal residuum product in accordance with the established practice.

For a better understanding of my invention reference is now made to theaccompanying drawing, which is a diagrammatic. view of an apparatussuitable for carrying the invention into effect.

Referring particularly to .the drawing the apparatus in general maycomprise a crude flash tower I, an evaporator 2, a viscosity breakingfurnace 3, a vapor phase cracking furnace 4, a soaking drum 5, afractionator 6 together with pipe lines, pumps, gauges, receiving drums,accumulator tanks and other appurtenant equipment for carrying out theprocess as hereinafter described.

Fresh heavy charging stock such as crude oil, after preliminary heatingto a distilling temperature, for example, by indirect heat exchange withhot products resulting from subsequent cracking steps, or after havingbeen heated in a directly fired coil,'or both, is forced throughcharging line 1 by'pump 8 into the upper stripping section 9 of thecrude flash tower I, wherein lighter constituents thereof are separated'as vapors and passed off through vapor line H) and condenser intoreceiving drum l2, the condensate collected in'the receiving drum being,for example,

light :naphtha or low end point virgin gasoline.

The unvaporized liquid collecting in the base of the section 9 iswithdrawn through pipe l3, and passed into the intermediate portion ofthe second section M of the crude flash tower, wherein a furtherseparation into vaporsand liquids takes place. This further separationmay be accomplished'by additional heating or by reduction in pressure orboth. The additional heatingmay be accomplished by passing the liquidthrough an indirect heat exchange |5 wherein it obtains heat from otherproducts of the system, by passing the liquid through a separately firedcoil (not shown) or it may be accomplished by direct or indirect heatexchange with a stream of highly heated vapors as will be explained morefully hereinafter.

The vapors generated travel upwardly through the section l4, and thoseremaining uncondensed at the top of this section pass off through vaporline I6 and condenser into receiver iii, the

distillate so collected being, for example, heavy Y naphtha which it isdesired to reform. An intermediate condensate collects on trap-out trayl9, and may be forced by pump 2!! through line 2| into the fractionator6 wherein it may serve as a refluxing medium, and may' at the same timebe placed in a position for circulation through the vapor phase crackingfurnace 4, as will be explained more fully hereinafter or it may bepassed directly through line 22 to an acqi lml ator phase.

tank 23 which receives vapor phase cracking stock.

The unvaporized liquid is withdrawn from the bottom of the section M ofthe crude flash tower through pipe 24.

The several sections of the crude flash tower or stripper l are providedwith bubble trays, baffles or other contacting means, as shown in thedrawing, in accordance with the usual practice.

The lower portion of the section 64 serves as a tar flashing chamber, aswill be explained hereinafter.

Reference numerals 25, 25 and 2'! indicate re-. fluxing lines throughwhich cool oil from an external source may be introduced for cooling andrefluxing purposes in the well-known manner. Alternatively, indirectcooling coils may be placed in the tower to accomplish the same purpose,

or cooling may be supplied in any well-known manner.

The unvaporized liquid reduced crude withdrawn'from the bottom ofsection l4 through conduit 24, passes to anaccumulator tank 28 fromwhich it is forced by pump 29 through the heating coil 3|] located inthe viscosity breaking furnace '3, from which the oil emerges, afterhaving been subjected to mild cracking or viscositybreaking treatmentprincipally for the purpose of producing additional quantities of lightclean gas oil stock suitable for cracking in the vapor phase, and isforwarded through transfer line 3| into the upper portion of evaporator2 above the trap-out tray 32 wherein separation of vapors from liquidresidue takes place. Valve 33 is inserted in the. transfer line 3| tocontrol the relative pressures in the viscosity breaking furnace andevaporator. The vapors pass updrawn through pipe 31 and condenser 38,the

condensate formed being collected in receiver 39. This condensate willbe gasoline of the desired end point. It may be used by itself, or itmay be combined with the light naphtha derived from the crude flashingoperation and collected in the receiver I2. Either or both'of thesedistillates may be stabilized, if desired, or be subjected to any othersuitable treatment to give them the selected characteristics.

Reflux condensate collects in the base of the bubble tower 6, is removedthrough conduit 43, and passed to accumulator tank 23 from whence it isforced by pump 4| through line 42 into .a cracking coil 43 in the vaporphase furnace 4, wherein it is raised to a cracking temperature andsubjected to conversion, preferably in the vapor The resulting crackedproducts emerge from the heating coil 43 and travel through transferline 44 into the soaker or reaction chamber 5, wherein they undergofurther conversion as a result of their contained heat, preferably undersubstantially the same pressure as held on the "wardly through theevaporator, undergoing partial condensation therein, this condensationbeoutlet of the heating coil. The digested products emerge from thesoaker through conduit 45 having pressure control valve 46, into thelower portion of the evaporator 2, wherein these products undergoseparation into vapors and liquid residue. The soaker 5 may beby-passed, if desired, in which case the desired digestion may beeffected within the heating coil 43 and a portion or all of the crackedproducts fromthe heating coil 43 may be passed directly through line 41,which merges with line 45 in front of reducing valve 46, into theevaporator 2.

The heavy naphtha collected in the receiver I8 is directed through theconduit 48, 'under'pressure generated by pump 49, through the naphthareforming coil located in the vapor phase furnace 4, wherein the naphthais raised to a high cracking temperature sufficient to cause theconversion thereof into higher anti-knock gasoline components. Theresulting reformed products are transferred from the coil 59 through theline 5|, having pressure control valve 52, into the lower portion of theevaporator 2.

Heavy gas oil condensate formed in the upper portion of the evaporator 2together with unvaporized products from; the heating coil 30, introducedinto the evaporator through line 3! collects in the trap-out tray 32located at an intermediate level in the evaporator 2, and is withdrawntherefrom through pipe 53, which leads to an accumulator tank 54, fromwhich it is withdrawn by pipe and forced by pump 56 through a heatingcoil 51 located in the viscosity breaking furnace 3. In this coil theoil is raised to cracking temperature and subjected to conversion intolighter products, including lighter gas oil suitable for cracking athigher temperatures in the vapor phase cracking coil 43. The resultingcracked products pass through the transfer line 58, having pressurecontrol valve 59, into the lower portion of the evaporator 2, andtherein undergo separation into vapors and liquids similarly to thecracked products already discussed.

A refluxing line Gil-is shown for supplying cooling fluid from anexternal source to the evaporator 2 and another line BI is shown forproviding cooling fluid to the top of the fractionator 6, in well-knownmanner. Indirect cooling coils might be used for accomplishing the samepurpose, in which event the cooling fluid might be the fresh chargingstock, whereby the charging stock would be raised in temperature to aidin the distillation thereof. The evaporator 2 is provided with baffleplates, bubble trays, or other suitable contacting means in a well-knownmanner. I have indicated all of the cracked products from the severalcracking and reforming coils 43, 59 and 51, as entering the evaporator 2through separate connections. Instead all of the pipes 45, 5| and 59might merge into a common connection leading into the evaporator.Cooling oil can be introduced into the shaker adjadent the outletthereof and likewise into the various transfer lines, for fluxingpurposes, in a well-known manner, if desired, so as to inhibit thedeposition of coke. Likewise any suitable cooling arrangement may beprovided for maintaining the temperature of the liquid collecting in thebase of the evaporator 2 at a suitably low value to prevent deleteriouscoke deposition therein.

The liquid residue collecting in the base of evaporator 2 is withdrawnthrough conduit 52, having pressure reducing valve 63, and is introducedinto the lower section 64 of the crude flash tower I, wherein itundergoes distillation or separation into vapors and unvaporizedresidual stock or tar, by Virtue of its contained heat, and

by reduced pressure effected by means of reduc-v ing valve 63. Ifdesired additional heat may be supplied to the liquid residue either byindirect heat exchange with hot products of the system or by means of adirectly fired coil in lieu of or in conjunction with reduction inpressure.

The vapors liberated in the lower section 54 of the flash tower may bewithdrawn through line 65, provided with valve 66 and introduced intothe intermediate section l4 wherein it directly contacts with freshcharging oil undergoing distillation andjthe heat of the vapors sointroduced utilized directly in carrying out the distillation.

In accordance with this procedure the heavier constituents of the vaporsso introduced will be condensed in the lower portion of the intermediatesection l4 below the trap-out tray. l9 and will be passed, along withthe topped or reduced crude, to the accumulator tank 28 which collectscharging stock for the coil 33 and an intermediate condensate formedfrom the vapors so introduced will be collected with fresh oilcondensate in trap-out tray 59, from whence it will pass to accumulatortank 23 and/or the fractionator 5. The heavy naphtha constituents ofthese vapors will be withdrawn, with the heavy naphtha constituents or"the original chargingstcc. through line [6, passing to the accumulatortank l8 which supplies charging stock to the reforming coil 5%.

In'accordance with one phase of my invention,

however, the vapors liberated from the residue in the bottom section 64of flash tower i are not caused to directly contact with fresh oilundergoing distillation as before described but are withdrawn fromsection 64 through line 6? and after being condensed in condenser 69 maybe forced by means of pump 68 to the upper portion of the evaporatortower 2,'above the trap-out tray 32 and be subjected to fractionation inthe upper end of the evaporator 2 and in the fractionator 5 along withthe other cracked vapors liberated in the evaporator as beforedescribed.

If desired a portion or all of the condensate from condenser 69 maypass, via line I!) and pump H directly to the accumulator tank 54 whichsupplies charging stock to the heating coil 51. A by-pass line isprovided around the condenser 69 so that a portion or all of the vaporsmay be introduced directly into the evaporator 2. If

' desired, a separate fractionating tower may be substituted for thecondenser 59 and the vapors separately condensed and fractionated into,a heavy gas oil condensate which may be passed to accumulator tank 54 orto thetop of the evaporator 2, a light gas oil condensate which may bepassed to the top of evaporator 22 or into fracticnator 6 or may bepassed directly to the accumulator tank 23, and a light distillatefraction which may be passed into the top of fractionator 6 or beseparately collected.

The unvaporized tarry residuum from the bottom section 34 of the flashtower l is withdrawn from the system through line 72.

The various conditions, such as temperature, pressure, time oftreatment, and the amount of conversion which should be effected duringa single passage of the oil through the respective heating coils underwhich my invention may be practiced to the best advantage are sointer-related and so dependent upon external factors, such as characterof the original stock and the quality and specifications of the finalproducts, that they cannot be prescribed with certainty to cover allcases. From a relative point of view, the cracking conditions, such asthe outlet temperature, for the heating coils 30, 51, 43 and 50 shouldbe increasingly drastic in the order mentioned. Conversion per pass andrate of heat input will be usually in the order of coils 51, 30, 43and50.

As an aid in carrying out the invention to the best advantage thefollowing examples of temperatures, pressures, conversion per pass andother conditions are given. It will be understood, however, that theseexamples are intended merely for general guidance and are not insertedfor the purpose of limiting the invention to the particular valuesgiven.

V For example, when treating common crude oils, such as Mid-Continentcrude or crudes of similar composition, to produce gasoline meetingstandard specification, such as gasoline having an endpoint of about 400F. and having an octane value of about C. F. R.M. (Cooperative FuelResearch-Motor Method) the tem-' perature at the outlet of thevis-breaking coil 30 may be of the-order of the SUD-850 F., the outlettemperature of the coil 5! may be of the orderof 850-925 the outlet ofheating coil 43 may range from 900-1000 F. and the outlet temperature ofthe coil 50 may be of the order of'1000-1100 F.

As a specific example, when processing Mid- Continent crude having agravity of about 37 A. P. I. to produce 400 F. end point gasoline havingan octane value of approximately 70 (C. F. R. M.) the outlet temperatureof the heating coil 30 may approximate 850 F., that of the heating coil51 may approximate 900 F., that of the heating coil 43 may approximate975 F. and the outlet temperature of the reforming coil 50 mayapproximate1050 F.

ciently low to prevent substantial coke deposition and may be in'theneighborhood of about 800 F. The temperature at the top of theevaporator should be controlled soas to condense heavy gas oilconstituents of the vapors within the upper region of the evaporator.For example, the top temperature of the evaporator may be controlled tocondense constituents boiling above 650-700 F. The top temperature ofthe fractionator may be controlled to produce gasoline of desired endpoint.

The fresh oil before being introduced into the upper section 9 of theflash tower I may be preheated to a temperature in the neighborhood ofBOO-400 F. and may be subsequently heated, either by direct contact withvapor products from the bottom section 64 of flash tower l, and/or byadditional heating to a temperature approximating 650-700 F.

The pressures maintained in various parts of the equipment is largely amatter of individual preference depending to some extent on the qualityof end products desired. The whole equipment may be under substantiallyuniform pressure except for the necessary difierential to cause the flowof products as hereinbefore described and may range from atmospheric toseveral hundred pounds per square inch. In certain respects,particularly in the distillation and vaporization equipment, pressure isreciprocal to temperature in that by reducing pressure the same effectmay be obtained as by increasing the temperature and consequen'tly'bymaintaining the products issuing from the heating coils undersubstantial pressure, successive reductions in pressure may be used incarrying out subsequent distillation and vaporization. Furthermore, bymaintaining the heating coils in which cracking takes place undersubstantial pressure, the amount of fixed gases formed during thecracking may be reduced.

, As a'guide in carrying out my invention to better advantage, thepressure in the evaporator 2 may be maintained, for'example in theneighbor hood of 200 pounds per square inch and the pressure in thefractionator 6 slightly lower.

' The outlet pressure on all of the heating coils may be substantiallythe same, and may be slightly in excess of the pressure maintained inthe evaporator or may be considerably in excess thereof so thatreduction in pressure,'by means of reducing valves in the transfer linesmay be utilized to aid in carrying out the vaporization. Also the lowersection 64 into which the cracked residue from the bottom of theevaporator 2 is introduced is preferably maintained at a pressurematerially below the pressure in the evaporator by means of reducingvalve 63 in-line 62 so that the cracked residue can be distilled by itscontained heat. a

In order to avoid excessive gas loss and improve the anti-knockproperties of the reformed gasoline it-is ordinarily deemed desirable tomaintain the oil passing through the reforming coil 50 under arelatively high pressure, such as an outlet pressure of from about 500to about 700 pounds persquare inch. The outlet pressure of any one ormore of the remaining coils may vary from slightly in excess ofevaporator pressure to relatively high pressure such as from 500 to 700pounds persquare inch.

The extent of conversion, during a single passage of the charging oilsthrough the respective cracking and viscosity breaking coils intogasoline constituents, or in other words the amount of conversion perpass, may be used to control the cracking and viscosity breakingconditions in the. respective coils. L

As a guide for controlling the cracking condi-' tions, such astemperature, time of treatment, and rate of heat input, the followingexamples are given.

For example, the conditions within the viscosi ty breaking coil 30 maybe controlled so as to convert from 10% to 20% of the original reducedcrude charge into gasoline constitutents preferably in the neighborhoodof 15%. In this connection it will be understood that the amount ofgasoline formed during passage of the oil through this coil is ofsecondary importance since the principal purpose of this treatment is toproduce suitable stock for the vapor phase'coil 43 wherein the oil issubjected to more suitable conditions for the production of gasoline.The amount of gasoline formed during passage of the oil through coil 30does, however, in a measure, indicate the amount of conversion of theoil into gas oil crack:

ing stock. In cases where vapors from the tar flashing drum, forming thebottom section 64 of flash tower I are not commingled with crude beingdistilled in the intermediate section I the amount of conversion in coil30 may be somewhat increased without introducing coking troubles.

The coil 51 may be controlled so as to convert from 6% to 15%,preferably about 10% of the charging stock into gasoline constituentsand coil 43 may be controlled to eifect from about 15% to 25%, or more,of the charging stock into gasoline, preferably about 20%.

By carrying out the process as .hereinbefore described, it is possibleto effect the desired conversion of the several components of theoriginal fresh oil under the optimum conditions. The inclusion of thetrap-out tray 32 and the associated heating coil 51 assures that theheavy gas oil condensate, and unvaporized products from the crackingcoil 3% which are not suitable for cracking in the vapor phase furnaceon account of coke forming tendencies, can be separately converted underthe conditions best adapted to cause a maximum conversion thereof. Theprovision of the cracking coil 5'! also lightens the load on theviscosity breaking furnace 3B and not only permits greater throughput ofreduced crude in that furnace, but also limits the stock going throughthat furnace either strictly to virgin components or to a greaterproportion of virgin components and to components which are more nearlyof like characteristics. The viscosity breaking furnace 30 can,therefore, be operated under the best conditions for cracking the heavyreduced crude, while the heavy cracked condensate and unvaporizedproducts from coil 30 which are collected on trap-out tray 32 may beseparately converted under conditions best suited to theircharacteristics, the clean gas oil cracking stock from the base of thefractionator and the heavy naphtha from the crude flash tower beingseparately treated in individual furnace coils, to cause the desiredconversion thereof, under conditions properly selected for the stocks inquestion without consideration for other of the fractions.

If desired the cracked products from the viscosity breaking coil 30 maybe introduced into a separate evaporator, (not shown), and the bottomsfrom the separate evaporator combined with condensate from the trap-outtray 32 for treatment in coil 51. Thejvapors from the added evaporatormay be separately fractionated in order to form'gasoline distillate andlight clean gas oil condensate suitable for vapor phase cracking, andthe gasoline distillate so segregated can then be combined, either withor without previous reformation, with the cracked gasoline collected inreceiver 39 and/or the virgin light naphtha collected in receiver l2, toform a desired blended product. The heavy gas oil condensatecorresponding to gas oil condensed above the trap-out tray 32, may beretained with the bottoms in the added evaporator and be combined withcondensate from the tray 32 of evaporator 2 for treatment in coil 51;

While I have described my invention in connection with a specificapparatus illustrated diagrammatically in the drawing, it is to beunderstood that the invention may be carried out in various other typesof apparatus. For example, while I have shown two separate furnaces withtwo coils in each furnace it will be clear that all of the coils might,if desired, be mounted in a single furnace or that each coil might bemounted in a separate furnace. It will also be clear that the positionof the coils in the furnace and. the routing of the oil through therespective coils will be in accordance with established practices inthis respect: Also, if desired, additional soaking drums may be providedfor each of the coils 30' and 51.

1 It will be understood that various valves, such as shown on thedrawing but not referred to by referencachara'cters, and possibly othersnot shown, may be used for control purposes. Auxiliary heat exchangers,cooling coils, pressure, flow and temperature controllers and otherappurtenant apparatus have been omitted from the draw.- ing in theinterest of simplicity, but should be provided in accordance with bestestablished practice.

While the preferred embodiment has been described for illustrativepurposes, it should be understood that my invention embraces such othermodifications and variations as come within the spirit and scope thereofand that it is not my intention to limit the invention except asnecessary to distinguish from prior art.

In the appended claims I have attempted to define the invention inall'its various forms and it should be understood that it is not myinten tion to dedicate or abandon any novel features thereof.

I I claim:

'1. In a process for converting raw crude oil into lower boilinghydrocarbons suitable for mo-' tor fuel wherein the original raw crudeis initially distilled to separate therefrom a light virgin naphtha, aheavy virgin naphtha which is subsequently subjected to a reformingtreatment for the purpose of improving its anti-knock proper tiesthereof, a light gas oil fraction which is subjected to crackingtreatment to convert the same into motor fuel constituents, and a toppedor reduced crude, and wherein the products from the reforming treatmentand from said cracking treatment are separated into vapors and residualproducts in a common zone, the vapor fractionated to separate a heavygas oil condensate, a light gas oil condensate, and a desired distillateproduct; the improvement which comprises subjecting said topped crude toviscosity breaking treatment, removing lower boiling constituentsincluding a light gas oil from the remainder of said products resultingfrom the viscosity breaking treatment, combining heavy gas oil resultingfrom the first-mentioned cracking treatment with said remainder,subjecting said composite mixture to separate and independent crackingtreatment, and separating a desired distillate product from the productsresulting from said last-mentioned cracking treatment.

2. A method of producing motor fuel from raw crude oil which comprisesinitially distilling said raw crude oil to vaporize lower boilingconstituents therefrom, separating a light gas oil condensate from thevapors so separated, heating the unvaporized reduced crude to aviscosity breaking temperature While passing in a confinedstream througha heating coil, thereafter introducing the products into an enlargedzone wherein vapors and liquid products separate, fractionating saidvapors, separately collecting light gas oil condensate and a desireddistillate product, Withdrawing unvaporlzed constituents and heavy gasoil conment, heating the combined-light gas oil condensate stock to arelatively high cracking temperature compared'to said last-mentionedcracking temperature while passing in a confined stream through aheating coil, thereafter introducing the products from said last-namedheating coil into said enlarged zone below the point of withdrawal ofunvaporized constituents and heavy gas oil condensate wherein vapors andliquid products thereof separate, withdrawing unvaporized residue fromthe bottom of said enlarged zone, distil- 3. A method of producing motorfuel from raw crude oil which comprises initially distilling said rawcrudeoil to vaporize lower boiling constituents therefrom, separating alight gas oil condensate from the vapors so separated, heating theunvaporized reduced crude to a viscosity break-' ing temperature whilepassing in a confined stream through a heating coil, thereafterintroducing the products into an enlarged zone wherein vapors and liquidproducts separate, fractionating said vapors, separately collectinglight gas oil condensate and a desired distillate product, withdrawingunvaporized constituents and heavy gas oil condensate from said enlargedzone, heating said withdrawn products to a cracking temperature whilepassing in a confined stream through a heating coil, thereafterintroducing the products from said last-named heating coil into saidenlarged zone below the point of withdrawal of said unvaporizedconstituents and heavy gas oil condensate wherein vapors and liquidproducts thereof separate, fractionating s'aid last-named vapors withsaid second-mentioned vapors, in a common fractionating zone, combininglight gas oil resulting from the initial distillation of the raw crudewith light gas oil condensate resulting from said viscosity breaking andcracking treatment, heating the combinedlight gas oil condensate stockto a relatively high cracking temperature compared to saidlast-mentioned cracking temperature while passing in a confined streamthrough a heating coil, thereafter introducing the products from saidlast-named heating coil into said enlarged zone below the point ofwithdrawal of unvaporized constituents and heavy gas oil condensatewherein vapors and liquid products thereof separate, withdrawingunvaporized residue from the bottom'of said enlarged zone, distillingthe unvaporized residue withdrawn from said enlarged zone and utilizingheat of vapors resulting from said last-named cracking treatment in theinitial distillation of said raw crude oil.

4. A method of producing motor fuel from raw crude oil which comprisesinitially distilling said raw crude oil to vaporize lower boilingconstituents therefrom, separating a light gas oil condensate from thevapors so separated, heating the unvaporized reduced crude to aviscosity breaking temperature while passing in a confined stream 7through a heating coil, thereafter introducing the ing unvaporizedconstituents and heavy gas oil condensate from said enlargedzone,heating said withdrawn products to a cracking temperature while passingin a confined stream through a heating coil, thereafter introducing theproducts from said last-named heating coil into said em large'd zonebelow the point of withdrawal of said unvaporized constituents and heavygas oil condensate wherein vapors and liquid products thereof separate,fractionating said last-named vapors with said second-mentioned vapors,in a common fractionating zone, combining light gas oil resulting fromthe initial distillationof the raw crude with light gas oil condensateresulting from said viscosity breaking and cracking treatment, heatingthe combined light gas oil condensate stock to a relatively highcracking temperature compared to said last-mentioned crackingtemperaturewhile'passing in a confined stream through a heating coil,thereafter introducing the products from said last-named heating coilinto said enlarged zone below the point of withdrawal of unvaporizedconstituentsand heavy gas oil condensate wherein vapors and liquidproducts thereof separate, withdrawing unvaporized residue'from thebottom of said enlarged zone, further distilling unvaporized residuewithdrawn from said enlarged zone, combining a distillate productresulting from said last-named distillation'with products passing tosaid second-named heating coil.

5. Themethod of producing motor fuel which comprises heating reducedcrude to a viscosity breaking temperature while passing in a confinedstream through a heating coil and thereafter separating the crackedproducts into vapors and liquids in an enlarged zone, Withdrawingunvaporized constituents and heavy gas oil condensate from said enlargedzone, heating the withdrawn products to a cracking temperature whilepassing in a confined stream through a second heating coil, thereafterintroducing the cracked products from said last-named heating coil intosaid enlarged zone below the point of withdrawal of said unvaporizedconstituents and heavy gas oil con densate to cause separation of thesaid cracked products last-mentioned into vapors and liquids,

fractionating said last-named vapors with said first-mentioned vapors ina common fractionating zone to form a reflux condensate and a desireddistillate product, heating reflux condensate so obtained to arelatively high cracking temperature compared to said last-mentionedcracking temperature while passing in a confined stream through a thirdheating coil, introducing the resulting cracked products from saidlast-named heating coil into said enlarged zone below the point ofwithdrawal of unvaporized constituents and heavy gas oil condensate,withdrawing unvaporized residue from the bottom of said en-' largedzone, flashing unvaporized residue withdrawn from the bottom of saidenlarged zone in a zone of reduced pressure and combining heavierconstituents of the flashed vapors with the reduced crude which ispassed to the first-mentioned heating coil.

6. The method of producing motor fuel whic comprises heatingreducedcrude to a viscosity breaking temperature while passing in a confinedstream through a heating coil and thereafter separating the crackedproducts into vapors and liquids in an enlarged zone, withdrawingunvaporized constituents and heavy gas oil condensate from said enlargedzone, heating the withdrawn products to a cracking temperature whilepassing in a confined stream through a second heating coil, thereafterintroducing the cracked products from said last-named heating coil intosaid enlarged zone below the point of withdrawal of said unvaporizedconstituents and heavy gas oil con-' densate to cause separation of thesaid cracked products last-mentioned into vapors and liquids,fractionating said last-named vapors with said first-mentioned vapors ina common fractionating zone to form a reflux condensate and a desireddistillate product, heating reflux condensate so obtained to arelatively high cracking temperature compared to said last-mentionedcracking temperature while passing in a confined stream through a thirdheating coil, introducing the resulting cracked products from saidlast-named heating coil into said enlarged zone below the point ofwithdrawal of unvaporized constituents and heavy gas oil condensate,withdrawing unvaporized residue from the bottom of said enlarged zone,subjecting unvaporized residue from the bottom of said enlarged zone toa flashing operation in a zone of reduced pressure, combining heavierconstituents of the flashed vapors with the reduced crude passed to thesaid heating coil first-mentioned and combining lighter constituentsthereof with the reflux condensate 10

